The present disclosure relates to a return to neutral (“RTN”) mechanism for a hydraulic axial pump and a hydraulic pump including such an RTN mechanism.
Hydraulic axial piston pumps are often hydraulically connected to a hydraulic motor through a hydraulic circuit. The pump is typically driven by an input shaft that connects to pulleys and belts. The pulleys and belts connect to an internal combustion engine. Axial pistons in the pump engage a pivotable swash plate and as the pump is rotated, the pistons engage the swash plate. Movement of the pistons results in movement of the hydraulic fluid from the pump to the motor. Pivotal movement of the swash plate is generally controlled by a trunnion arm that is connected via linkages to either a hand control or foot pedal mechanism that is operated by an operator of the vehicle that includes the hydraulic pump and motor.
The hydraulic pump described above has a neutral position where the pump pistons are not moved in an axial direction so that rotation of the pump does not create any movement of hydraulic fluid out of the pump. RTN mechanisms operate with the swash plate to return the swash plate to a neutral position when a force is no longer being applied to rotate the trunnion arm. Such devices can minimize unintended movement of the vehicle and can also return the pump to neutral in the event of a vehicle operator no longer being able to engage the hand control or foot pedal mechanism that is connected through a linkage to the trunnion arm.